Polyurethane thermoplastic material and production process

ABSTRACT

The thermoplastic polyurethane material has the general formula I ##STR1## (1&lt;f&lt;500; 1&lt;f&#39;&lt;15; R and R&#39;=alkyl or aryl) and X has formula II ##STR2## (2&lt;n&lt;140; 1&lt;(n&#39;+n&#34;)&lt;51). The process for the preparation thereof comprises reacting a polyether-polycaprolactone block copolymer having a molecular weight ranging from 1000 to 6000 of formula IIa ##STR3## with a chain extender of formula HO--R&#39;--OH and a diisocyanate of formula OCN--R--NCO.

DESCRIPTION

The invention relates to a thermoplastic polyurethane material ofgeneral formula I: ##STR4## where f is an integer ranging from 1 to 500;f is an integer ranging from 1 to 15; R and R' are the same or differentand stand for alkyl or aryl groups and X is a polyether-polycaprolactoneblock copolymer having a molecular weight ranging from 1000 to 6000 andhaving formula II ##STR5## where n is an integer ranging from 2 to 140;n' and n" are integers the sum of which ranges from 1 to 51.

This polyurethane is particularly useful in extrusion, injection andmelt coating operations.

The thermoplastic polyurethane materials of the present invention offerthe advantage over the known ones that they have a relatively lowhardness (they can attain values of around 86 shore A) and haverelatively high melting or softening points, of around 220°.

The invention also relates to a process for the preparation of the abovementioned compound, the process comprising reacting apolyetherpolycaprolactone block copolymer of formula IIa ##STR6## with achain extender of formula HO--R'--OH and with a diisocyanate of formulaOCN--R--NCO where R, R', n, n' and n" have the meaning given above. Saidchain extender is preferably 1,4-butanediol and said diisocyanate isdiphenyl methane 4,4'-diisocyanate, toluene 2,4- and 2,6-diisocyanate,dicyclohexyl methane 4,4'-diisocyanate or3-isocyanomethyl-3,5,5-trimethylcyclohexyl isocyanate.

The reaction is also preferably conducted by mixing equimolecularamounts of diisocyanate with said chain extender and saidpolyetherpolycaprolactone block copolymer of formula II, said latter twocompounds being in a proportion ranging from 1:1 to 15:1.

It is contemplated that mixing be continuous at a flowrate ranging from200 to 1500 kg/h of total weight of the ingredients and that it shouldtake place in an extruder at a temperature ranging from 150° to 350° C.and with a mean dwell time ranging from 45 seconds to 2.5 minutes.

The reaction is conducted preferably in the presence of metalcomplexbased catalysts proper to the urethane reactions, particularlyderivatives of tin and/or bismuth.

The invention also relates to the compound of formula IIa and to aprocess for the preparation thereof, which is conducted by reacting apolypropylene glycol with terminal hydroxy groups mainly of secondarynature and of formula III ##STR7## where n has the meaning given above,with ε-caprolactone of formula IV ##STR8##

The thus obtained copolymer comprises terminal hydroxy groups mainly ofprimary nature in an amount in excess of 60% of the total hydroxygroups.

This reaction comprises the following steps:[a] charging thepolypropylene glycol and the ε-caprolactone in a reactor at roomtemperature under a flow of nitrogen; [b] heating to a temperatureranging from 100° to 200° C. under a flow of nitrogen for a time rangingfrom 0.5 to 1.5 hours; [c] adding a metal-complex catalyst up to atemperature ranging from 160° to 250° C.; and [d] maintaining thereaction for a time ranging from 2 to 8 hours.

Some examples of the processes to which the invention relates are givenbelow.

EXAMPLE 1 Preparation of a Formula II Polyol

A reactor at room temperature, with nitrogen flow and mechanicalstirring is charged with 2,000 kg of polypropylene glycol and 2,000 kgof ε-caprolactone.

The raw reaction mass is heated to 120° C. and held at this temperaturefor an hour so as to remove the water from the starting products.

The raw reaction mass is heated to 200° C. and at this temperature 15ppm of tin derivative metal-complex catalyst are added. The temperatureof the reaction mass is rapidly raised to 220° C. and the evolution ofthe reaction is checked by gas chromatography. Once the reaction iscompleted after 5 hours, the reaction mass is cooled to 120° C. anddischarged from the reactor at this temperature. The product obtained isstored under a nitrogen atmosphere.

The maximum heat given off at T=200° C. is 9.93 W/kg; the total heatgiven off by the reaction being 87.48 kJ/kg. An adiabatic temperaturerise of 43.2° C. is calculated for the process.

The reaction power profile shows that the process increases the rate upto a maximum level at a point close to half the reaction time.

EXAMPLE 2 Preparation of a Thermoplastic Polyurethane Material

1,250 kg of diphenyl methane 4,-4'-diisocyanate, 360 kg of butanedioland 4,000 kg of the polyether-polycaprolactone block copolymer preparedaccording to Example 1 are taken. These products are continuously mixedat a rate of 600 kg/h in a twin screw extruder having a configurationproper to that of a reactor, at a temperature which is held between2000° and 300° C. with a mean dwell time ranging from 1.5 to 2.0minutes.

On exiting from the extruder it is cut, cooled and dried and packaged inbead form under standard temperature and humidity conditions. During theprocess 100 ppm of metal-complex catalysts are used.

What is claimed is:
 1. Thermoplastic polyurethane material of generalformula I: ##STR9## where f is an integer ranging from 1 to 500; f is aninteger ranging from 1 to 15; R and R' are the same or different andstand for alkyl or aryl groups and X corresponds to formula II ##STR10##where n is an integer ranging from 2 to 140; n' and n" are integers thesum of which ranges from 1 to
 51. 2. A process for the preparation of athermoplastic polyurethane material of general formula I: ##STR11##where f is an integer ranging from 1 to 500; f' is an integer rangingfrom 1 to 15; R and R' are the same or different and stand for alkyl oraryl groups and X corresponds to formula II ##STR12## where n is aninteger ranging from 2 to 140; n' and n" are integers the sum of whichranges from 1 to 51, the process comprising reacting apolyether-polycaprolactone block copolymer having a molecular weightranging from 1000 to 6000 and having formula IIa ##STR13## where n, n'and n" have the meaning given above, with a chain extender of formulaHO--R'--OH and with a diisocyanate of formula OCN--R--NCO where R, R',have the meaning given above.
 3. The process of claim 2, wherein saidextender is 1,4-butanediol.
 4. The process of claim 2, wherein saiddiisocyanate is diphenyl methane 4,-4'-diisocyanate, toluene 2,4- and2,6-diisocyanate, dicyclohexyl methane 4,4'-diisocyanate or3-isocyanomethyl-3,5,5-trimethylcyclohexyl isocyanate.
 5. The process ofclaim 2, wherein the reaction is conducted by mixing equimolecularamounts of said diisocyanate with said chain extender and saidpolyether-polycaprolactone block copolymer of formula II, said lattertwo compounds being in a proportion ranging from 1:1 to 15:1.
 6. Theprocess of claim 5, wherein the mixing is continuous at a flowrateranging from 200 to 150 kg/h of total weight of the ingredients andtakes place in an extruder at a temperature ranging from 150° to 350° C.and with a mean dwell time ranging from 45 seconds to 2.5 minutes. 7.The process of claim 2, wherein said reaction is conducted in thepresence of metal-complex based catalysts proper to the urethanereactions.
 8. The process of claim 7, wherein said metals are tin and/orbismuth.
 9. A polyether-polycaprolactone block copolymer of formula IIa,##STR14## where n is an integer ranging from 2 to 140; and n' and n" areintegers the sum of which ranges from 1 to
 51. 10. A process for thepreparation of a polyether-polycaprolactone block copolymer according toclaim 9, of formula IIa, ##STR15## where n is an integer ranging from 2to 140; and n' and n" are integers the sum of which ranges from 1 to 51,which comprises reacting a polypropylene glycol with terminal hydroxygroups mainly of secondary nature, of formula III ##STR16## here n hasthe meaning given above, with ε-caprolactone of formula IV ##STR17##there being obtained a copolymer having terminal hydroxy groups mainlyof primary nature, in an amount in excess of 60% of the total hydroxygroups.
 11. The process of claim 10, wherein the reaction comprises thefollowing steps:[a] charging the polypropylene glycol and theε-caprolactone in a reactor at room temperature under a flow ofnitrogen; [b] heating to a temperature ranging from 100° to 200° C.under a flow of nitrogen for a time ranging from 0.5 to 1.5 hours; [c]adding a metal-complex catalyst up to a temperature ranging from 160° to250° C.; and [d] maintaining the reaction for a time ranging from 2 to 8hours.